Method of and device for charging explosive projectiles



INVENTOR MICHEL PRECOUL M. PRECOUL Aug. 4, 1959 METHOD OF AND DEVICE FOR CHARGING EXPLOSIVE PROJECTILES Filed Dec. 17. 1954 carried out in practice.

United States Patent METHOD OF AND DEVICE FOR CHARGING i EXPLQSIVE PROJECTILES Michel Prcoul, Paris, France, assignor to Societe Technique de Recherches Industrielles et Mecaniques, Strim, Paris, France, a French society t This invention relates to methods and means for charging explosive projectiles.

Experience teaches that the charging of explosive projectiles, especially hollow-charge projectiles, when efiected by applying the hitherto known'casting methods employed for charging ordinary projectiles, occasions many disadvantages, such as irregularity in the perforating force, reduction in disruptive power, etc.

1 It is an essential object of this invention to provide method of charging hollow-charge projectiles with cast explosive, whereby on the one hand the disadvantages broadly set forth hereinabove may be avoided, and, on the other hand, a maximum perforating force may be obtained notably for a hollow charge of predetermined weight and caliber. .1

Other features and advantages of this invention will appear as the following description proceedswith reference to the attached drawing and illustrating diagrammatically the manner in which the invention: may be Of course, it will be understood that the example shown in the drawing and described hereafter .is solely illustrative and should not beconstrued as limiting the purpose of the invention, as many modifications and alterations may be madewithout departing from the spirit 'and scope of the invention.

.The. examples described hereafter refer to the use of a binary mixture containing 50% of hexogen and 50% of tolite. a

. .The inventionis .also applicableto 'hexogen-tolite mixtures having other proportions than 50/50, as well as to any. other explosives, for example pentolite, hexogen, tolite, aluminium, etc. v. 4 a v :zThe charging method of this invention is carried out by casting the product directly through the base into the body of. theprojectile, and its essential features are as follows: 1 A

(1).T'lhe casting is eifected with a substantial feed re: serve; s r

(2). High-temperature heating (at-a temperature -at least equal ,to the melting point of the explosive) ofthe charged projectile during a relatively long time period, so as. to enable the heaviercrystals (hexogen crystals for example), to decant or form-a sedimentary layer adjacent to'the front portion of the hollow charge;

(3.) First clearing orpre-clearing of obstructed passage; 1

(4) Re-filling after the aforesaid pre-clearing; and 1 (5 Devices for insulating and heating the unavoidable constricted portion of the charge.

Reference-twill now. be made to the specific example illustrated in the drawing, wherein:-f r Figure-l: shows in diagrammatical longitudinal section a projectile at the end'of the charging operation, and Figure '2 shows also in =diagrammatical longitudinal section-"buton a greater scale 'the upperportion 'of the projectile duringthe pr-clearing operation.

, 2,897,714 Patented Aug. 4,

The projectile 1 is provided at its base end with aconventional filling funnel 2 having fitted thereon, according to this invention, an extension member 3 of. a capacity substantially equivalent to, or greater than, the inner capacity of the chamber 4 in which the explosive product cast into the projectile is received.

Before effecting the charging operation each projectile is heated at about C. during atime period of from 10 minutes to 60 minutes, for example, to remove any trace of moisture from the insideand raise. the temperature of the body, funnel and extension assembly at least to the melting point of the explosive. With this procedure any sudden cooling, contraction, etc. of the jets of cast ex-. plosive is avoided during the casting operation.

The molten explosive (for example a hexogen/tolite mixture) is stored in a constant-temperature vat, forexample heated at 95 C. preferably through automatic temperature adjusting means.

The explosive product is brought to a pasty condition and stirred continuously so as to keep it in a perfectly homogeneous state. 5'

Prior to effecting the casting operation the projectile bodies are provided, as shown in Fig. 1, with a cotton or Woolen sleeve 5 surrounding their throttled base portions. These sleeves 5 are heated beforeha'nclto 95 C., for example; as a substitute for cotton or woolen sleeves; ringshaped members of light-alloy, bronze, steel or'oth'er metals may be used; in both cases the sleeves or like members ,are pre-heaited with the aforesaid assembly. The purpose of this arrangement is toretard the cooling of the explosive ,in the throttled region, thereby reducing any pipe formation. J

Then the casting operation is carried out while constantly maintaining the explosive mixture at a relatively high temperature (for example 95. C.) and stirring it to maintain its homogeneousness. The extension member 3 is filled to of its height or moresoas to contain an explosive mass of a volume greater than the volume of the cavity of the projectile to be .filled with explosive whereby there is obtained a reserve for the feed of explosive in order to pour it into the latter.

Upon completion of the charging step, the projectile bodies are introduced into a drying oven and heated for a relatively long period, ranging for example from 10 minutes to 60 minutes, at a relatively high temperature, for example 95 C. This operation has a twofold purpose: J

(a) avoiding pipe formation by increasing the fluid condition of the charge during a relatively long time period, and e i (b) enabling themixture to decant or form a sedimentary layer (for example, of hexogen/tolite) so that the heavier product (for example hexogen) willbe deposited at the bottom, i.e. adjacent to the .front portion of the hollow charge, the extra hexogen being removed from the funnel extension constituting the reserve of the heavier product. Y 4

With this method it is thus possible to enric the charge proper located in the cavity of theprojectile body, notably in the front portion thereof, due to the fact that the hollow-charge lining is thus surrounded directly with a more powerful, active and heavier explosive (for example hexogen) although the initial mixture (forexample hexogen/tolite) is weaker and lighter, but possesses better melting and casting properties. 1

Consequently, the method of charging projectiles according to this invention makes it possible, from an initial less powerful but more easily handled product, to obtain amore powerful, active and concentrated charge.

After the cooling step carried out as the projectiles are e'xtractedfrom the drying ovenin which the decanting step has taken place, the next step of the charging method is efiected which consists in a first clearing operation or pre-clearing.

' This operation":.isiillustratedEin Fig. 2 and ,itsnpurpose isito'suppress systematically the cavity or pipe formations likelyto occur, especially coaxially and adjacent to the top-of the ,hollow charge. Therefore, this pre-clearing step :isreitected, ,according'to this invention, in the throttled region of the base and ascloseas possible to thelining, overta'diameter approximating :the inner diameter of. the base: orifice. For example, the depth of penetration of rtherpre-sclearing :member may bexadjustedtoi within a few millimetersor about of the-caliber from .the lining.

Upon completion .of this. .pre-clearing :step, the .chargingioperation is terminated in accordance with'zthe process set forth hereinabo ve, that.:is ,the-extension member3 is placed again in communication with .the opening forthe pouringof the projectile so that theicavity created by the preliminary flow maybe filled, the assembly of the extension. projectile being heated for a prolonged period, .for example 20 to 60 minutes, at ahigh'temperature, 95 C., for example.

, Then, the projectiles thus charged are ready for the final, conventional clearing operation designedto form the cavity for receiving the compressed or rammed priming explosive.

The hollow-chargezexplosivescharged according to the method o'fthis inventionare-characterized by a maximum penetrating power and a perfect regularity. The value ofa chargethus efiected is calculated moreparticularly as afunction of the high specific gravityof the cast mixture filling. the projectile cavity. Thus, in the case of a hexogen/tolite mixture 50/50 charged according to this invention the :mixturespecificgravity is as high as 1.67 or 1.68.

In those cases where the explosive employed does not provide the minimum specific gravity required, a method of generally improving this specific gravity is also provided byv this invention, which consists in the procedure set forth. hereafterr To exemplify the -method a practical embodiment thereof'will be described with particular reference to a hexogen/tolite mixture.

Again, it is pointed out that other explosive mixtures and .proportions may be employed withoutdeparting from the spirit and scope of the invention.

The primary mixture molten in the melting vat will consist, according to the invention, of:

.(A) aquantity 2a of a hexogen/tolite mixture as in stock, made of 50% hexogen and 50% tolite, and

:(B) a quantity aoftolite.

The-resultingintermediate mixture 3a is extremely fluid and melts very easily.

According to this invention, a quantity a of, for example, pure hexogen in granules, crystallized or not, is added to the above intermediate in'ixture 3a after the latter has melted completely.

The resulting enriched mixture of weight 411 (enriched to 100% but still having a final hexogen/tolite content of 50/50) constitutes the product to be finally cast into' the projectiles.

Of course, it would not constitute a departure from the principles of this invention to obtain and use a mixture having other final proportions than the 50% hexogen and 50% tolite mentioned hereinabove, as these proportions may be conditioned by the desired final. results (density, perforating power, weight, casting properties, etc.). In this case the proportions 2a, a, etc. will also. vary.

The pure hexogen in granules and crystallized or not employed for the enriching step should comply with certain screening requirements,- according to this. invention.

I Byway of example it may be stated that when pure granu- "lated hexogen is employed it should be retained to the extents of in the Afnor (Association Francaise de Normalisation) Screen No. 26 which corresponds to a mesh opening of 0.315 mm. of which 75% are retained in the Afnor Screen No. 28 which corresponds to a mesh opening of 0.50 mm.

Under the same conditions, when pure crystallized hexogen is employed, up to 95% should be retained in the Afnor Screen Not 26, and. of these, 65% should be retained in the Afnor Screen No. 27 which corresponds toa' mesh opening of 0.40mm.

The enriched mixture-thus constituted is subsequently utilized and charged by employing the charging procedure of this-invention, as set ,forth hereinabove.

What I claim is:

1. A method of charging by casting the cavity of a projectile body of the hollow-charge type having a liner comprising placing above the casting opening of the projectile to. becharged a mass ,of explosive supply, said opening having the same axis as the lining axis of-the hollow charge, said explosive supply comprising a molten explosive containing in suspension in the .form of .finely divided .solid particles, a more powerful and more dense explosive than said molten explosive, the volume ofsaid'mass being greater than. the cavity tobe filled, placing said mass in communication through said axialcasting' opening with the interior of said projectile, subjecting said ma-ss and said filled projectile to a prolongedheating at a temperature at least equal to the melting temperature .of. the molten explosive but less than the melting temperature of the .solidexplosivein .suspem sion tor a period sufiicient to settle the more dense .explosive about the liner and then finally cooling the assernb1y:formed by said mass and ,said'projectile.

.2. A methodof charging by casting the cavity .ota projectile body of the hollow-charge type having a liner. comprising placing .above the casting opening of the projectile to be charged a mass .of molten tolite con? taining insuspension hexogen distributed in said mass in the .form ,offinely divided particles, said opening having-the same axis as the lining axis of the hollow-charge, the volume of said mass being greater than the cavity to be filled, placingv said mass in communication with the -interior of said projectile through the intermediary of said casting opening, subjecting when. said charge has been completed said mass and said projectile to a prolonged heating \at a temperature at least equal to the melting; temperature of said tolite but less than .the melting temperature of said hexogen 'for a period sufficient to settle the hexogen about the liner and then finally allowing the assembly formed by said mass and said projectile to ,cool.

3. A method of chargingasset. forth in claim 1 com prising after cooling separating said explosive mass su-. perposed upon the axial casting opening from said projectile, removing the solidified explosive in the region located at the :upper portion of the filled cavity of the projectile and around the axis ,of said cavity, replacing an explosive mass above said casting opening, again placing said mass in communication withv the interior of said projectile through the intermediary of said casting opening and heating said mass and said projectile for a prolonged time at ,a temperature at least equal to the melting temperature of said molten explosive but less than the melting temperature of the solid explosive in suspension and then finally allowing the assembly to cool.

4. A method of charging as set forth in claim 1 of a projectile of the hollow-charge type having a lining of generally conical configuration comprising after cooling removing the solidified explosive in the region located above said' lining along a diameter substantially equal to thatof the casting opening of the projectile and at a distance starting from the top of said lining less than the caliber. of the-projectile, replacing the superposed References Cited in the file of this patent UNITED STATES PATENTS Knight et a1. Feb. 28, 1933 Lawson Aug. 5, 1952 FOREIGN PATENTS France Nov. 14, 1936 Great Britain Apr. 18, 1951 

